Square law force measuring device



Feb. 24, 1953 F. 1 coRBlN 2,629,259

SQUARE LAW FORCE MEASURING DEVICE Filed oct. 11, 194e 2 SHEETS- SHEET 1j INV T l BW fq ATTORILIEY Feb. 24, 1953 Filed Oct. 11, 1946 F. L.QQRBIN SQUARE LAW FORCE MEASURING DEVICE 2 Sl-IEETS-SHEET 2 4 NyENTOR fBY AT1-ORM Patented Feb. 24, 1953 SQUARE LAW FORCE MEASURING DEVICEFrancis L. Corbin, Chatham, N. J., assignor to Pitometer LogCorporation, New York, N. Y., a

corporation of New York Application October 11, 1946, Serial No. 702,819

Claims.

My invention relates to a square law device, that is, a mechanism whichgives a reading proportionate to the square root of a force appliedthereto. While such a device may have numerous applications, one of thechief uses thereof is in connection with either a flow meter or a shipslog, both of which devices measure the relative speed of a liquid, aflow meter measuring the velocity of liquid flowing through a pipe,while a ships log measures the speed of the ship through the water.Inasmuch as the pressure produced by movement of liquid relative to aPitot orifice is proportionate to the square of the speed, it isnecessary to extract the square root of this pressure in order to obtaina reading directly proportionate to the speed.

In the following my invention will be described in connection with aships log although, as above indicated, it is to be understood that itis not limited to this particular use.

Further objects and advantages of my invention will be apparent from thefollowing description considered in connection with the accompanyingdrawings which form a part of this speciiication and of which:

Fig. 1 is a front view of an apparatus in accordance with my invention;and

Fig. 2 is a cross-sectional view taken on the line 2-2 of Fig. 1.

Referring to the drawings, reference character I0 designates a baseplate upon which the square law mechanism is mounted. A bracket I2 issecured to the rear of the plate and supports a pair of axiallyexpandable and contractible Sylphon bellows I4 and I6. The interior ofthe bellows I4 is connected by means of a conduit system I8 with thedynamic orifice 20 of a rod 22 which is disposed outside the hull of theship and well below the water line, the oriiice 20 facing forward sothat, when the ship is moved forwardly it moves relative to the water inthe direction indicated by the arrow 24. The bellows I6 is connected bymeans oi the pipe system 26 with the static orice 28 formed in the rod,this orice opening in a plane which is parallel to the direction ofmovement of the ship.

The lower movable heads of the bellows I4 and I6 bear against pins 30carried by a balance arm 32, the two pins 30 being disposed on oppositesides of a rotatable shaft 34 to which the balance arm is secured. Thisshaft is rotatably mounted in suitable bearings carried by brackets 36and 38 mounted on opposite sides of the base plate I0, shaft 34extending through the base plate. A tension spring 40 is secured betweena bracket 42 carried by the mounting plate and the end of 2 arm 32 whichis on the same side of shaft 34 as is the bellows I6.

Fixed to the shaft 34 on the forward side of the plate I0 is an arm 44.A pair of divergent arms 46 is connected to the upper end of arm 44, thelower spaced ends of these arms rotatably carrying bevelled gears 43 and50. These gears mesh with a pair of bevelled gears 52 and 54 which arerotatably mounted on the shaft 34. The gear 52 is rigidly xed to an arm56, while the gear 54 is rigidly secured to a spur gear 58. The spurgear meshes with a spur gear of the same diameter which is ixed to ashaft 62 rotatably mounted in the plate I0 and in the bracket 38. An arm64 is rigidly secured to the shaft 62 so as to turn with the gear 60. Atension spring 66 is secured between the arms 56 and y 64, the efectivelengths of these arms being equal.

Gear 60 also meshes with a pinion gear 68 which is xed to a shaft I0rotatably mounted in the base plate and in a bracket 12. The forward endof shaft 'I0 carries a pointer 'I4 which is arranged to move over astationary scale 'I6 which is calibrated in units of speed, such asknots.

Gear 58 meshes with a pinion 18 which is connected through the geartrain including gears 80, 82, 84 and 86 with the driving shaft 88 of areversible electric motor 90.

The upper end of the assembly comprising the arms 44 and 46 carries apair of movable contacts 92 and 94 which are disposed between fixedcontacts 96 and 98. One terminal of a suitable source of electriccurrent is connected by means of a conductor |00 with a terminal of themotor 90, while a conductor |02 connects the other side of the source ofpower with the movable contact points 92 and 94. The fixed contacts 96and 98 are connected by means of conductors |04 and |06, respectively,with the two other terminals of the motor 00. The construction of thismotor is such that when current is supplied to it through conductors |00and |04 it rotates in one direction, while when current is suppliedthrough contacts |00 and IE5 it rotates in the opposite direction.

A pair of electro-magnets |08 and ||0 are disposed on opposite sides ofthe arms 44 and 46, the latter carrying a block of magnetic material||2. One terminal of each of the electro-magnets is connected by aconductor I|4 to the conductor |00, while the other terminal of themagnet |08 is connected by the conductor I I6 .to the conductor I 06leading from the xed contact 98, while the other terminal of the magnet||0 is connected by the conductor I I8 to the conductor |04 leading fromthe fixed contact 96.

The above described device operates as follows.

In the drawings the parts are shown in the positions which they occupyat Zero speed of the ship. Under these conditions the luid pressureacting through the dynamic oriiice will be equal to that acting throughthe static criilce 28, and will be dependent upon the draft of the ship.If the draft remained constant it would not loel necessary to provide astatic orice, but inasmuch as the draft varies in accordance with theloading of the ship, the static orice and bellows I 6 serve to balancethe fluid pressure resulting from the liquid head so that the differencein pressures acting on the two bellows is equal to the dynamic pressureresulting from movement of the dynamic orifice through the water.

As above stated, when the ship is stationary, there is no dynamicpressure and hence the .pressures exerted by the two bellows are equal.A s the force resulting from these pressures are applied to the balancearm 32 at points equi-distant from the shaft 34, they produce no turningmoment on the balance arm. However, the spring produces a constantturningr moment tending to rotate the arm and hence the shaft 34 in aclockwise direction as viewed in Fig. 1. This tends to rotate theassembly consisting of the ams 44 and 4'6 and the differential bevelledgears 48 and 5i) in a clockwise direction. Inasmuch as these gears meshwith the bevelled gears 52 and 54, such motion could take place only ifone or both of these gears were rotated in a clockwise direction asviewed in Fig. l. If the gear 52 were rotated in a clockwise direc--'tion the arm 46 would be turned in the same direction, but if the gear54 and hence also the gear 58 were turned clockwise, it would result inrotating the gear 6D and hence the arm G5 counterclockwise. Such motionsin opposite directions .of the two arms would increase the tension ofthe spring 66. As a matter of fact, it is the turning moments producedby the tension of this spring acting through the arms and 64 andtransmitted through the gearing to the balance arm 32, which balance theturning moment produced by the spring 4] acting directly on the balancearm 32. It will be noted that the turning moment produced by the spring66 depends upon the angular positions of the arms 516 and 64. If boththese arms extended exactly vertically downwardly the spring wouldproduce no turning moment whatsoever on either gear 52 or the gear 68,because the line of force would coincide with the. line connecting thecenters of these two gears. The maximum turning moment is obtained whenthe arms 56 and 64 'are normal to this line, as shown in the drawing,and the turning moment produced by the spring 166 for other positions ofthe arms varies substantially inversely with the square of the anglebetween the arms and the horizontal for arm position varying from thoseshown in the .drawing to a position of approximately 30 from thehorizontal counterclockwise. In other words, if the angle with thehorizontal is doubled, the turning moment is decreased four times. Itwill also be noted that the tension of the spring 65, as distinguishedfrom the turning moments produced thereby, remains constant for allpositions of the arms. This is due to the fact that inasmuch as thesearms are of equal length and are turned in the same direction throughequal angles, the distance between their ends remains constant.

As above stated, the turning moment applied to the arm 32 by the spring66 when the arms 56 and 64 are in the position shown, namely at an angleof with the intersection of their center lines, is equal and opposite tothe turning moment applied to arm 32 by the spring 4U. Ii the ship nowgets under way, dynamic pressure is produced in the orice 23 and iscommunicated through the pipes I8 to the bollows i4. The additionalforce now exerted by the bellows 4 on the balance arm 32 in the samedirection as the force applied to the arm by the spring 6e unbalances4the system and causes this arm and the shaft 313 to pivot slightly in acounterclockwise direction, thus turning the yarms 4.4 and 46 slightlycounterclockwise and closing the circuit to the motor 90 through thecontacts S2 and 95. This causes the motor to operate in the properdirection to rotate the spur gear 58 in a clockwise direction, whichdrives the spur Vgear 68 and the arm 64 in a counterclockwise direction.Inasmuch as bevelled gear 54 is xed to spur gear 58 it also rotatesclockwise and drives the bevelled gear 52 counterclockwise through thebevelled gears 48 and 50. This in turn causes the arm 5B to turncounterclockwise. Inasmuch :as the ratio between the gears 58 and 60 isthe same as the ratio between the gears 54 .and 52, namely unity, thetwo arms 56 and 64 move through the same angle. As above stated, thisdoes not change the tension of the spring 86, but it does decrease theturning moment exerted .by the spring in an amount proportionate t0 thesquare of the angle through which the two arms are turned.

inasmuch as the dynamic pressure produced at the orifice 28 isproportionate to the square of the speedand the rotation of the arms 56and 613 is proportionate to the square of the turning moment produced bythe spring 65, the rotation of the gear 60 is directly proportionate tothe change in speed of the ship. Consequently, the rotation of thepointer T4 caused by the rotation of the gear 60 indicates the speed 'atwhich the ship is travelling.

Actually, motor 98 does not run continuously until the balance in thesystem is restored inasmuch as, as iswell known, this would result inover-regulation and hunting. The closing of the circuit through thecontacts 92 and 96 energizes the electro-magnet H0 which thereuponattracts the armature ||2 carried by the lever 44 so as to again openthe circuit. In the meantime, lthe motor B0 is operated in the .properdirection to restore the balance. As soon as the circuit is open theelectro-magnet H0 is deenergized and if the operation of the motor hasno-t been sufcienrt to completely restore the balance, the circuit willagain be completed through the contacts 92 and S6 and the cycle will berepeated. Thus, the system is .brought baci: into balance by means of aseries of steps.

In the event that the speed of the ship is reduced the force exerted bythe bellows I4 is reduced, and hence the spring 48 turns the lever 32 aslight amount in a clockwise direction. This serves to complete thecircuit through the contacts S4 and QB, thus causing the motor tooperate in the opposite direction so as to turn the arms 56 and 54clockwise. This in turn increases the turning moment exerted by thestationary tension spring 66 until it balances the new turning momentapplied to arm 32.

If the electro-magnets |08 and H0 were not provided the motor 8D wouldcontinue to operate until the turning moment produced -by the spring 65had been decreased sufficiently to balance the resultant turning momentapplied to the arm 32 bythe bellows and the spring d, whereupon the arm44 would be returned to its neutral position, thus opening the contactsand stopping the motor.

' It will be noted that the change in elongation of the springs lill and5S is very slight and need be sufficient. only to open and close theelectric contacts. Consequently, it is not necessary to employaccurately calibrated springs and no error is introduced into the systemdue to improperly calibrated springs. In practice this has been found tomore than compensate for the slight error resulting from the fact thatthe change in turning moment produced by the spring et is not exactlyinversely proportionate to the square of the angle between the arms 5eand 5e and the horizontal.

While I have shown and described one more or means for applying aturning` moment to said lever proportionate to the square of a variableo,

value, means for applying a substantially con stant turning moment tosaid lever, a beveled gear carried by said shaft with its axis ofrotation normal to the axis of the shaft, a pair of coaxially mountedbeveled gears meshing with the do first-mentioned gear, a pair of armsturnably mounted on parallel axes, motion transmitting means betweensaid pair of gears and said arms for causing one of said arms to turn inthe opposite direction from one gear of said pair and the other arm toturn in the same direction as the other gear of said pair, and formaintaining said arms substantially parallel to each other, spring meansstressed between said arms, means for turning said arms to thereby varythe turning moment resulting from said spring means and transmittedthrough said motion transmitting means, the gears, and said shaft tosaid lever and means movable in direct proportion to the angle ofmovement of said arms.

2. In a device of the class described, a rotatable shaft, a balancelever secured to said shaft, means for applying a turning moment to saidlever proportionate to the `square of a variable value, means forapplying a substantially constant turning moment to said lever, abeveled gear carried by said shaft with its axis of rotation normal tothe axis of the shaft, a pair of coaxially mounted beveled. gearsmeshing with the first-mentioned gear, a pair of arms turnably mountedon parallel axes, motion transmitting means between said pair of gearsand said arms for causing one of said arms to turn in the oppositedirection from one gear of said pair and the other arm to turn in thesame direction as the other gear of said pair, and for maintaining saidarms substantially parallel to each other, spring means stressed betweensaid arms, a pair cf fixed electrical contacts, an electrical Contactmovable with said lever between said pair of contacts, a reversiblemotor controlled by said contacts, driving means between said motor andsaid arms for turning the latter to thereby vary the turning momentresulting from said spring means and transmitted through said motiontransmitting means, the beveled gears and said shaft to said 6 lever,and mean-s for indicating the angle through which said arms are turned.

3. In a device of the class described, a rotatable shaft, a balancelever secured to said shaft, means for applying a turning moment to saidlever proportionate to the square of a variable value, a spring forapplying a substantially constant turning moment to said lever inopposition to the first-mentioned turning moment, a first pair of bevelgears rotatably mounted to turn on an axis normal to and intersectingythe axis' of said shaft, a second pair of bevel gears rotatably mountedon said shaft and meshing with said first pair of gears, a first armconnected to turn with one gear of said second pair, a second armturnably mounted about an axis parallel tothe axis of said first arm,reverse gearing between the other gear of said second pair and saidsecond arm for causing the latter to turn in the opposite direction fromsaid other gear and to maintain said arms substantially parallel to eachother, spring means stressed between said arms, means for turning saidarms to thereby vary the turning moment resulting from said spring meansand transmitted through said reverse gearing, said bevel gears and saidshaft to said lever and means movable in direct proportion to the angleof movement of said arms.

4:. In a ships log, a differential Pitot member having a dynamic oriceand a static orifice, a rotatable shaft, a balance lever secured to saidshaft, a pair of Sylphcn bellows applied to said lever at pointsequidistantly spaced from said shaft, means for transmitting fluidpressure from said orifices to the respective bellows, a spring forapplying a substantially constant turning moment to said lever inopposition to the turning moment applied thereto by the bellowsconnected to said dynamic orifice, structure secured to said shaft, afirst pair of -bevel gears rotatably mounted on said structure on anaxis normal to and intersecting the axis of said shaft, a second pair ofbevel gears rotatably mounted on said shaft and meshing with said firstpair of gears, a rst arm connected to turn with one gear of said secondpair, a second arm turnably mounted about an axis parallel to the axisof said rst arm, reverse gearing between the other gear of said secondpair and said second arm for causing the latter to turn in the oppositedirection from said other gear and to maintain said arms substantiallyparallel to each other, spring means stressed between said arms, meansfor turning said arms to thereby vary the turning moment resulting fromsaid spring means and transmitted through said reverse gearing, saidbevel gears and said shaft to said lever and means movable in directproportion to the angle of movement of said arms.

5. In a ships log, a differential Pitot member having a dynamic orificeand a static orice, a rotatable shaft, a balance lever secured to saidshaft, a pair of Sylphon bellows applied to said lever at pointsequidistantly spaced from said shaft, means for transmitting fluidpressure from said orices to the respective bellows, a spring forapplying a substantially constant turning moment to said lever inopposition to the turning moment applied thereto by the bellowsconnected to said dynamic orifice, structure secured to said shaft, arst pair of bevel gears rotatably mounted on said structure on an axisnormal to and intersecting the axis of said shaft, a second pair ofvbevel gears rotatably mounted on said shaft and meshing with said firstpair of gears, a first arm connected to turn with one gear of saidsecond pair, a second arm turnably mounted .aboutan yaxis parallel tothe laxis of said iirst arm, reversegearing between the other, gear 4,ofsaid second pair and said second'armfor causing thelatter'to turn in theopposite'direction from said other gear and tomaintain saidfarms subfvstantially parallel to eachother, springV means stressed between zsaidarms, a pair of fixed electrio contacts, an electrical Contact movablewith said lever between said pair `of contacts, a reversible motorv.controlled by said contacts, driv- 10 ing means betvveenisaid motorand said arms for turning the latter to thereby vary the turning momentresulting from Asaid spring means and transmitted through 4said reversegearing, said bevel gears and said shaft to said lever, indicating meansuniformly calibrated in units of Vspeed and operable in response to theturning of said arms.

l IfRANCIS CORBIN.

REFERENCES CITED The following references are of record in the file ofthis patent: l y Y UNITED `ESTATES PATENTS

